This invention pertains to apparatus and methodology associated with the collection of human heart-related anatomical signals—both electrical and audio. It also relates to special signal-collection and signal-output processing. While preferred and best-mode implementations of the invention are referred to throughout herein as involving the heart, it is recognized that other kinds of bio-information may be desirable to collect. Accordingly, reference to the heart in this disclosure should be read and understood to apply to other human anatomy realms.
Prior art collection of ECG-electrical information for diagnostic purposes is very well known. Known also is the fact that collected, heart-activity-produced sound information provides useful diagnostic data. With respect to the matter of sound collection, since the early days of phonocardiography, accelerometers were used to detect heart sounds on the chest wall. All that those accelerometers did was to measure the impulse of sound waves perpendicular to the chest surface. Since the energy of heart vibrations (S1, S2, S3, S4, and murmurs) is transported mostly by shear surface waves, a uni-directional detection apparatus, i.e. a uni-directional accelerometer, will be limited to registering the energy component perpendicular to the surface of the chest wall only.
In one approach to signal collection as proposed by the present invention, both sound (multi-axial) and electrical (ECG) signals are collected simultaneously from a common anatomical site so that ECG signals, and important heart-produced sound signals, such as the S-sound signals known as the S1, S2, S3 and S4 sounds, can be correlated in different ways to produce accurate, useful diagnostic information in a manner which significantly rivals prior art techniques to get at the same information.
Simultaneous, common-site sound and ECG signal collection may be performed selectively with or without axial symmetry, depending upon the physical configuration chosen for signal-collection structure made in accordance with the invention. Attachment to the anatomy, such as to the thorax, may be accomplished in different ways, such as via a suitable bio-gel/adhesive, or by way of a vacuumizing (suction) arrangement.
The proposed signal-collection structure may utilize, selectively, different specific types of ECG electrode structures, with sounds being gathered, as by one or more small accelerometers(s), along three orthogonal (X, Y and Z) axes preferably either by a multi(three)-axis accelerometer, or by three, orthogonally (angularly) oriented, uni-axis accelerometers. The mentioned Z-axis is normal to the surface of the anatomy. Using a multi-axis accelerometer with appropriate sensitivity and load on the chest wall, or correspondingly multiple unidirectional accelerometers with their measurement axes arranged in different orientations to the chest wall, it becomes possible to capture the maximum of the detectable heart sound energy on the surface of the human thorax.
X and Y sound components may be processed and employed: (a) to give certain important X and Y sound analyses that furnish very useful S-sound information; (b) to minimize extraneous noise interference with desired signal information; (c) to give a sense of anatomical surface directionality to guide lateral repositioning of the signal-collection structure so as to maximize the acquisition of Z-axis sound information; and (d) to accomplish other desirable things. Extraneous noise interference can come from many sources, such as from digestive sounds, respiration related sounds, and vibrations due to muscle tension, etc.
With regard to S-sound information, the point of maximum impact (PMI) for vibrations on the chest wall caused by sounds originating in the heart (S1, S2, S3, S4, and murmurs) is classically detected by auscultation. Since many frequency components of the heart sounds, especially the ones related to S3 and S4 heart sounds, are in the inaudible frequency range, and are damped due to absorption of sound energy in human flesh, auscultation results are sometimes inaccurate and simply impossible to perform in certain body positions, especially in the supine position. An additional consideration, addressed by the multi-axial sound collection approach proposed by the present invention, involves the detection of heart sounds in body positions which cannot easily be altered.
In accordance with the invention, direct electrodes/sensors (a) may be integrated or made separable from one to another, (b) may be made reusable or discardable, (c) may carry self-contained internal signal-processing structure, and/or (d) may be made connectable to adapters which carry signal-processing structure. Signal-processing structure, per se, which is employed as generally described herein, is not detailed herein inasmuch as such structure may be constructed in various manners that are well known to those skilled in the art using conventional technology. An on-board electronic memory unit may be provided in a patient-specific-device to capture collected ECG and sound data for future reference. Such a future reference capability can enable serial monitoring of a particular person to furnish valuable risk stratification information.
Appropriate filter circuitry, which may be entirely conventional in construction, may be employed in signal-processing structure to provide what is known as an apexcardiogram output signal.
The many and various features and advantages, including those just mentioned, which are offered by the invention will become more fully apparent as the description which now follows is read in conjunction with the below-described drawings.